This has had several goals:
- a target suitable for x86 and armh providing a rather
  minimal set of base xorg packages and generic drivers;
- task-oriented targets for graphics use cases:
  + "desktop" means rather 2D focus with 3D being welcome
    or even essential but not performance critical, thus
    "a slower driver is fine as long as it does work";
  + "3d" means specific 3D performance being critical,
    that is "no 3D means no use at all".

Regarding the free and proprietary 3D-capable drivers:
the previous idea was to split out some common ground
and then add the contenders on top of that; the current
approach is based on the observation that the live images
requiring proprietary NVIDIA/AMD drivers *by default*
are usually of not much use with hardware that lacks
proper 3D acceleration (like Tseng cards) or the driver
support for that (like Matrox these days).

Intel videodriver makes for a special case though:
it is both free and top-notch performer.

Thanks sem@ and boyarsh@ for discussion.

PS: xorg-drv-{keyboard,mouse,void} dropped;
those who need these can usually help themselves.